Randomly extinguishing light fixture

October 8, 2008 7:53 PM

Why did my light fixture start turning off and on randomly? How do I fix it?

The light fixture above our kitchen table just started turning itself off and on* randomly. It's quite annoying. (Darnit, there it goes again!)

This fixture is a pretty standard one where there's a piece that's embedded in the ceiling (where the bulbs go) and a translucent glass cover. It holds two bulbs and is attached to a dimmer switch. Currently the bulbs are two incandescents at 60W each.

My suspicion is that some part of it is overheating, though I'm not totally sure of this. When the problem first happened, it only had one working bulb and was set to a dim light. I replaced the bulb figuring it had blown out, and took the opportunity to replace the other one at the same time, so it probably runs a lot hotter now.

The light can stay on for 45-60 minutes or so. Then it'll turn itself off for about 15 minutes. If I leave the switch on, it'll eventually pop back on... and turn off again... ad infinitum.

Circuit breakers are not tripping in the electric box.

I'm no electrician and am not afraid to hire one, but since I bought this house I've learned that a lot of things aren't all that hard to fix yourself. I'm hoping that's the case with this, and if not then I hope to at least have a clue so an electrician can't fleece me.

* - I know "turn itself off and on" is probably not the accurate term. There's no digital switch or anything that reflects the problem -- just an analog dimmer. But "extinguishes and rekindles itself" doesn't sound right either.

posted by rouftop to home & garden (8 answers total)

First thing I'd do is pull the fixture off the ceiling and make sure all the wires are tight, replace any wire nuts, etc. If everything is fine there, then try replacing the dimmer switch. It's possible that having both lights on increases the amount of current going through the switch and that's causing the failure.

Then again, I've been replacing lights, switches, and outlets since I was 12 years old. It's not that dangerous, but make sure the circuit breaker is off before fooling around up there. You only make that mistake a dozen times or so :)
posted by sbutler at 8:02 PM on October 8, 2008

This is not good. Loose wires, intermittent connections, these are things that lead to electrical fires. Most likely the contacts where the bulb screws in are bad, either with oxide on them or the little tab at the base has lost its flex. Bending out the tab and cleaning of the oxide with a pencil eraser or sandpaper (power off) might fix that. If it is a loose wire inside, that is the real danger, although if you find it the cure is usually just a turn of the screwdriver.
posted by caddis at 8:12 PM on October 8, 2008

I think it's the dimmer.
posted by lee at 8:27 PM on October 8, 2008

You're probably getting a loose connection into a cycle of thermal expansion and contraction. I've had this problem in a house of a certain vintage where part of the wiring was aluminum.

Tightening connections is a good first step. An electrician may be a good second step.
posted by dws at 10:08 PM on October 8, 2008

Sounds heat-related, and in your situation that points to the dimmer.
posted by SteveInMaine at 3:36 AM on October 9, 2008

When you say the fixture is "embedded in the ceiling," I take that to mean recessed lighting. Most all recessed fixtures have some kind of internal thermostat that turns the light off when it gets too hot. Try lower wattage bulbs or CFL's.
posted by lost_cause at 7:23 AM on October 9, 2008

Hi,
I knew "embedded in the ceiling" would get me in trouble. It's not recessed. I mean something like this.
posted by rouftop at 10:41 AM on October 9, 2008

dws came closest. I tried replacing the dimmer, but that had no effect. I pulled down the fixture, but couldn't see anything that I felt comfortable mucking with. So in came the electrician.

He told me there are three main causes for this behavior: 1) dimmer switch has gone bad, 2) loose connection somewhere, 3) bad thermal coupler. This fixture didn't have a thermal coupler, and I proved #1 wasn't the problem, so he went with #2. As it turned out, it was a simple twist of one pair of wires that fixed the problem. I'm annoyed that I didn't find it, but then again he worked without turning off the circuit box so he could figure out exactly what was going on, which I wasn't willing to do.

Thanks all.
posted by rouftop at 7:10 AM on October 21, 2008